Noise discrimination control circuit utilizing a volume control thermionic amplifier circuit



Jan. 7, 1964 J. H. KUCK ETAL 3,117,284 NOISE DISCRIMINATION CONTROL CIRCUIT UTILIZING A VOLUME CONTROL THERMIONIC AMPLIFIER CIRCUIT 4 Sheets-Sheet 1 Filed Feb. 25, 1944 FIG. 2

INVENTORS JOHN H. KUOK BY ROBERTj/I. THQYE 77 AT$ORNEY 3,117,284 NOISE DISCRIMINATION CONTROL CIRCUIT UTILIZING A VOLUME Jan. 7, 1964 J. H. KUCK ETAL CONTROL THERMIONIC AMPLIFIER CIRCUIT 4 Sheets-Sheet 2 Filed Feb. 25, 1944 m on UE AMY ET PL H E HM x mm T m 8:: 0 0 $2M 7. E s H mm 0 NE/ 8 MW m wa wo R L wMM JR m w L L L0 Z M m w a w MN b FWF 0. ma mm m w l ew w WM 2F L -M 6x 3 0 0 RFW a M 6 r n a F w a M 4 m w w m m 9 w w Jan. 7, 1964 uc ETAL 3,117,284

NOISE DISCRIMINATION CONTROL CIRCUIT UTILIZING A VOLUME CONTROL THERMIONIC AMPLIFIER CIRCUIT Filed Feb. 25, 1944 4 Sheets-Sheet 3 FREQUENCY RESPONSE OF AMPLIFIER BEFORE AFTER COMPRESSION msouavcrcrass PER ssaolvo INVENTORS JOHN H. KUOK BY ROBERT? THAYER I! 3,117,284 0N CONTROL CIRCUIT UTILIZING A VOLUME T I U c R I C F T. HI W Kw .T. m in NT mu IR MT w m0 S I D E S I M 9 1 7 m J 4 Sheets-Sheet 4 Filed Feb. 25, 1944 CURVE I 7M}! INOREJSHI 7O 2/ UV. INPUT C HUI!- INCREJSED TO HIV. INPUT m V. S E R P w a x M N w E m S w AMPLIFIER 7U SUDDENLY INCREASED mu: 8 250 CYCLE INPUT A5 A FUNCTION OF TIME cwws A 7w. INCREASED 710 Mm: INPUT OUNVE O URVE 4 m ma kaw wm A558 0.6 0.8 T [HE SE OONDS AMPLIFIER T0 .SUDOENLY INCREASED 250 CYCLE INPUT AS A FUNCTION OF TIME cum? .4 zauu mane-45m to 39m INPUT cum 5 zsuv. m/mssa mazwwmr cunvz c 2am INCREASED m mm INPUT INVENTORS JOHN H. KUOK BY ROBERT THAYER A ORNEY TIME SECONDS United States Patent M 3,117,284 NOISE DISCRIMINATION CONTROL CIRCUIT UTILIZINGA VOLUME CQNTROL THERMI- ONIC'AMPLIFIERsCIRCUllT- ,1: John Kuek, Silver-Spring;:Md-, and Robert H. Thayer, Washington, D.C., assign0rs; to the-.United= States; of Arnericaqas represented ;by..the Secretary-of the Na y Filed Feb..25, 1944, Ser. No.fl52 3,886

. .3 Claims. (@11328 3l65) This invention relates generally to improvements in thermionicv amplifying devices and more particularly to an improved compressionv circuit" especially adapted for use in the amplifier of aradio proximity ifuz/e. I

Steady noise may arise in such an amplifier frorn vibrations of tube elements which may be set up as a result ofharmonic forces arising from the combined spin .and yaw .of theprojectile when in flight. The wave effect? (movement of the projectile close to ocean waves) may likewise produce an undesirable noise signal. .It is there-v fore'the primary object of this invention to provide an improvedamplifier which will discriminate against' con tinuous noise; .so that :it will not give sufficient'output from a steady noise input/to fire a grid-controlled or nigger-acting arc tube of the thyratron type but will respondtora signal of. short duration; such as a ripple signal, for triggering such a tube;

Another object of the invention is to provide an ampli fier wherein the noise discrimination is accomplished by applying a'rectifiedportion ofthe output .voltage, through atime delay circuit, tothe grid of the first amplifier tube as negative bias. i j n A further object of the invention is to provide an arm plifier compression circuit wherein the compression takes effect in a time shorter than the normal arming time of 3,117,284 Patented Jan. 7, 1964 term groun here means the shell, or body, of the projectile. H n gr -'I he second amplifying tube 2 is coupled t o the output of the m i rqe en s ta d e out 9 h stub w i. h v h lw r i ig 1 sni r=r 4 11 e anode 1d of a diode 12. The fiiamenhor cathode, of the diode 12 is connected to ground by a. suitable conductor 13 which ground ,ter minalalso constitutes a negatiyeiter mina-l for the filament battery. As stated, the ground terminal is constituted byithe bo dy of the shell or projectile,

Theanode,11,of the diode 12 is also eonnectedto the meeting terminals of resistors Hand 15,. 'I 'he resistor cooperateswith the condenser 7 tQ,pI:OVld '8 time delay and to filter the current rectified by the diode, as ,will be described in detail hereinafter. The resistor lS will func i n to pe17m taleaking off of the charge of thecondenser 7 when there ,is a decrease in the rectified voltage from the diode. Iherefore adecreaseinlthejamountlof compression will follow a decrease in thelamplitude of the Signal V 4 V V. t The output of the amplifying tube 2 is also connected to the grid of a gas-containing thermionic tube, suchas a thy ratroin 16 through a coupling condenser 17, the grid;of' the thyratron being biased through. are sistor 18 and the plateiofsaid tuhe being connected in theeircuit withthe squib (not showri) or other firing rnea ns, and the plate battery. The plate, or B, hatteryjs connected to the plates of the amplifyingatubes through conductors 18",1 9 and 20', the conductor Ztl beingconnected tothe plate load resistor and to one't erminal of a screenlvolt the fuze, with the'result that noise. existing at the begin;

Still another object is to provide an amplifier which is so arranged that the gain isautomatically regulated, according to'the existing'noise level, and the probability of premature fuze operation due torandom noise thereby reduced. V I T Further objects of the invention, not mentioned herein above, will become evidentduring the course jof the following description, taken in conjunction with the ac compa'nyingdrawings, throughout the severaltvie ws of which like reference characters. designate similar .parts.

Iuthe drawings: h I FIG. 1 is a schematic View of the improved amplifier; HG. 2 is a schematic view showing. a slightly modified arrangement; I Q FIGS. 3 to 7 inclusive are curves showing performance of th'e circuit. 7 n v Referring now to the drawings, reference numerals 1 and Zdesignate amplifying tubes of the pentode type. In this connection it should be understood that tubes of other types may be used, if preferred. Thearnplifying tube 1 includes an input circuit comprising two condensers 3, t4

theresistor 6 and the ground. As will beunderstood'the age divider2121a, said divider including resistors 21 and 21a. The divider is so arranged that proper-voltage will be applied to the screen of the amplifying tube Suitable by-pass condensers 23 are ,connectedbetween the screens of the tubes 1 and 2' and the ground. a The operation of the inve ntion will new be briefly described; A signal entering the input circuit of the first amplifyingtube, 1 from the oscillator (not shown) will be impressed upon'the" control grid of said tube. The said signal will be amplified by tube l -a nd in turn Will become the input signal for the succeedingtube. This signal !will be amplified by thejs'cond amplifying tube, 2, and practically the full am'plitude of the' ar'iipli fied signal will be fed i nto the grid of tube 1;6, :tlirough the condensers 10 and 17. However, this condition exist only;mom entar ily, since a portion of this signal voltage is rectified by the diode 12, and this-rectified voltage is applied to the grid of the first t-ube,-througli-the delaycircuit, as negative bias. Due to the tact that this-delay circuit is employed, compressionwill not take place-untilafteithe desired time interval has passed. This time. intervalwill be of sufiicient duration to permit an'pple or pulse, signal to build up to suflicient' amplitude to trigger the thyraton, but will be shoft enough so that compression; discrimination against; continuous noise) will take effect before the firing oircuit'becomes armed. 'In this connection, it is desired to pointout that the c0ndenser 7 and the resistor 14 .serve not only-to provide a time dealay'but also to -filterthe rectified voltage. The divider 21-21a, as will be seen, provides suitable screen voltage for the first amplifyingtubeso that said tube 1-Willhave sharp cut-off characteristics. V v 'It' should .be understood that; although the values of resistorsandcondensers havebeen indicated-on the drawings, resistors and condensers of other values may be used if it is desired to vary the response of the circuit.

It should also be understood that compression will take effect in a time shorter than the normal arming time. Therefore, there is no possibility that the firing condenser will arm (charge to the value necessary to fire the squib) before the compression has had a chance to reduce the gain of the amplifier sufiiciently to render a noise pulse of even unusually great amplitude less likely to fire the thyratron.

The curves shown in FIGS. 3-7 show the performance of the improved circuit. More particularly, FIG. 3 shows both the initial output from suddenly applied signals and the output after compression takes effect. For example, an input of 13 millivolts, which initially was sufiicient to produce firing, produced only 52% of firing output after compression.

In FIG. 4, the frequency response, in terms of millivolts input necessary to fire the tube 16, is shown. One curve is the initial response to a suddenly applied input signal and the other curve indicates the steady input signal necessary. Thus, while a 13 millivolt initial signal at 250 cycles will fire the trigger tube, a steady noise of the same frequency would not fire said tube if it were less than 315 millivolts.

Motion pictures have been taken to show decay of output with time, and the curves in FIGS. 5, 6 and 7 were plotted from these pictures. FIG. 5 shows the response to suddenly applied signals of three different amplitudes. FIGS. 6 and 7 indicate the action taking place when the amplitude of steady signals is suddenly increased. Curve B of FIG. 7 indicates that, even with a steady noise input of 26 millivolts, the system could still be fired with an additional signal of 26 millivolts.

Although the circuit of FIG. 1 shows a diode rectifier, it should be understood that rectifiers of other types may be used. A compression circuit utilizing a copper oxide rectifier is shown in FIG. 2. In this view the resistor R-1 and condenser C-l serve the dual purpose of providing a time delay before compression takes effect, and of acting as a filter. Rectification of peak A.C. voltage is obtained if the discharge time constant of C-2, through the inverse resistance of the rectifier, is sufficiently long. As will be noted, a resistor corresponding to the resistor 15 is eliminated in FIG. 2 for the reason that the inverse resistance of the rectifier (copper oxide) is such that said resistor is unnecessary. Resistor R-2 is used with this rectifier to increase the plate load impedance. As in the circuit of FIG. 1, dividing resistances are used to provide screen voltage for the amplifier tubes.

As pointed out heretofore, the improved compression circuit will operate to suppress noise existing at the beginning of flight of a projectile. Thus, the arming condenser will be permitted to charge, with the result that repeated firings will be prevented, and a live fuze after five seconds will be assured. As indicated in the curves of FIGS. 5-7, compression takes effect in a time shorter than the normal arming time. Fuze failures, due to the wave effect, would be prevented for the same reasons. Also, as the gain is automatically regulated according to the existing noise level, the probability of premature detonation due to random noise will be greatly reduced. As was also pointed out in the objects at the beginning of this description, continuing noise, as would be produced by yaw and spin of the shell, could never fire the thyratron, but the fuze would still respond to a ripple signal, even though its sensitivity might be somewhat reduced. Thus, projectiles which might otherwise be ineffective would retain at least a portion of their effectiveness.

What is claimed is:

1. In an amplifier system for actuating a proximity fuze having a thyratron in response to transient type oscillatory target signals of a few cycles duration, a multiple stage low frequency amplifier having an inp t C rc and an output circuit, means for discriminating against continuous noise and intermittent single pulse noise to prevent undesired firing of said thyratron thereby, said means comprising a rectifier having the cathode thereof connected directly to ground to receive and rectify a portion of the amplifier output signal, a resistance-capacitance circuit directly connected between the output of said amplifier and the anode of said rectifier and a second resistancecapacitance circuit connected between the anode of said rectifier and the input of said thyratron, whereby the rectifier circuit provides an initial clipping action to the positive half of the first cycles of said amplifier output signal which is applied to the grid of said thyratron and causes said clipping action to disappear on subsequent cycles, a biasing circuit connected to said rectifier and to the input circuit of said amplifier to apply said rectified signal portion thereto as a negative grid bias, thereby diminishing the output of the amplifier, including a low pass filter means having a time-constant corresponding to said transient type oscillatory target signals of a few cycles duration, for limiting the rate at which the gain is reduced, whereby said target signals are translated without substantial reduction in gain while slowly increasing long duration signals are substantially reduced by action of said biasing circuit.

2. In an amplifier system for actuating a proximity fuze having a thyratron in response to transient type oscillatory target signals of a few cycles duration, a multiple stage low frequency thermionic audio-frequency amplifier having an input circuit and an output circuit, means for discriminating against continuous noise and intermittent single pulse noise to prevent undesired firing of said thyratron thereby, said means comprising a diode having the cathode thereof connected directly to ground to receive and rectify a portion of the amplifier output signal, a resistance-capacitance circuit directly connected between the output of said amplifier and the anode of said diode and a second resistance-capacitance circuit connected between the anode of said diode and the input of said thyratron, whereby the diode circuit provides an initial clipping action to the positive half of the first cycles of said amplifier output signal which is applied to the grid of said thyratron and causes said clipping action to disappear on subsequent cycles, a biasing circuit connected to the said diode and to the input circuit of said amplifier to apply said rectified signal portion thereto as a negative grid bias, thereby diminishing the output of the amplifier, including a low pass filter means having a time-constant corresponding to said transient type oscillatory target signals of a few cycles duration, for limiting the rate at which the gain is reduced, whereby said target signals are translated without substantial reduction in gain while slowly increasing long duration signals are substantially reduced by action of said biasing circuit.

3. In an amplifier system for actuating a proximity fuze having a thyratron in response to transient type oscillatory target signals of a few cycles duration, a multiple stage exclusively resistance-capacitance-coupled thermionic amplifier having a grid-controlled input circuit and an output circuit, means for discriminating against continuous noise and intermittent single pulse noise to prevent undesired firing of said thyratron thereby, said means comprising a rectifier having the cathode thereof connected directly to ground to receive and rectify a portion of the amplifier output signal, a resistance-capacitance circuit directly connected between the output of said amplifier and the anode of said rectifier and a second resistance-capacitance circuit connected between the anode of said rectifier and the input of said thyratron, whereby the rectifier provides an initial clipping action to the positive half of the first cycles of said amplifier output signal which is applied to the grid of said thyratron and causes said clipping action to disappear on subsequent cycles, a biasing circuit connected to the output of said rectifier and to the input circuit of said amplifier to apply said rectified I signal portion thereto as a negative grid bias, thereby diminishing the output of the amplifier, including a low pass filter means having a time-constant corresponding to said transient type oscillatory target signals of a few cycles duration, for limiting the rate at which the gain is reduced, whereby said target signals are translated without substantial reduction in gain while slowly increasing long duration signals are substantially reduced by action of said biasing circuit, and a high resistance bleeder resistor connected across said biasing circuit to dissipate said bias and thus restore the sensitivity of said input circuit after cessation of noise.

References {Zitcd in the file of this patent UNITED STATES PATENTS Farnham Sept. 1, Wohlfarth et a1. Sept. 5, Foster Apr. 9, Schonland Dec. 9, Foster Feb. 17, Hollingsworth Aug. 25, Thompson Nov. 10, Wellenstein et al Sept. 14, 

1. IN AN AMPLIFIER SYSTEM FOR ACTUATING A PROXIMITY FUZE HAVING A THYRATRON IN RESPONSE TO TRANSIENT TYPE OSCILLATORY TARGET SIGNALS OF A FEW CYCLES DURATION, A MULTIPLE STAGE LOW FREQUENCY AMPLIFIER HAVING AN INPUT CIRCUIT AND AN OUTPUT CIRCUIT, MEANS FOR DISCRIMINATING AGAINST CONTINUOUS NOISE AND INTERMITTENT SINGLE PULSE NOISE TO PREVENT UNDESIRED FIRING OF SAID THYRATRON THEREBY, SAID MEANS COMPRISING A RECTIFIER HAVING THE CATHODE THEREOF CONNECTED DIRECTLY TO GROUND TO RECEIVE AND RECTIFY A PORTION OF THE AMPLIFIER OUTPUT SIGNAL, A RESISTANCE-CAPACITANCE CIRCUIT DIRECTLY CONNECTED BETWEEN THE OUTPUT OF SAID AMPLIFIER AND THE ANODE OF SAID RECTIFIER AND A SECOND RESISTANCECAPACITANCE CIRCUIT CONNECTED BETWEEN THE ANODE OF SAID RECTIFIER AND THE INPUT OF SAID THYRATRON, WHEREBY THE RECTIFIER CIRCUIT PROVIDES AN INITIAL CLIPPING ACTION TO THE POSITIVE HALF OF THE FIRST CYCLES OF SAID AMPLIFIER OUTPUT SIGNAL WHICH IS APPLIED TO THE GRID OF SAID THYRATRON AND CAUSES SAID CLIPPING ACTION TO DISAPPEAR ON SUBSEQUENT CYCLES, A BIASING CIRCUIT CONNECTED TO SAID RECTIFIER AND TO THE INPUT CIRCUIT OF SAID AMPLIFIER TO APPLY SAID RECTIFIED SIGNAL PORTION THERETO AS A NEGATIVE GRID BIAS, THEREBY DIMINISHING THE OUTPUT OF THE AMPLIFIER, INCLUDING A LOW PASS FILTER MEANS HAVING A TIME-CONSTANT CORRESPONDING TO SAID TRANSIENT TYPE OSCILLATORY TARGET SIGNALS OF A FEW CYCLES DURATION, FOR LIMITING THE RATE AT WHICH THE GAIN IS REDUCED, WHEREBY SAID TARGET SIGNALS ARE TRANSLATED WITHOUT SUBSTANTIAL REDUCTION IN GAIN WHILE SLOWLY INCREASING LONG DURATION SIGNALS ARE SUBSTANTIALLY REDUCED BY ACTION OF SAID BIASING CIRCUIT. 